What you are talking about is automation of outbound payment, which is very much possible. But the requirement here is automation of inbound payment, like a merchant have on credit card payments. This is something inherently not supported by Bitcoin protocol and counted as consumer's advantage. Hence, even if n-lock is used, due to fund unavailability the payment may not take place.
Well, I'm not worried about the customer making the fund unavailable (which could happen for a bank account too), I am more worried that the customer forget to pay if it is not automated. (Not a problem if you have one customer, but it does not scale)
If you ask him to spend a 12 month paiement on a 1 of 2, you know that, except if he decides it, the paiement will be done.
On the merchant side, if the paiement is not done, you can stop providing the service, it makes unsubscription from your service very easy.
You just know that he needs to consciously decide it.
However, I think a 1-of-2 wallet may be more useful than it initially appears. The difference between a shared private key and a 1-of-2 wallet is that it becomes provable which party spent the coins.
Imagine that I offer a Bitcoin Visa card for my customers. My customers deposits coins to a 1-of-2 wallet whenever they like and I authorize Visa payments depending on whether their balance is sufficient. If a customer tries to buy a new bike for $1,000 with his Bitcoin Visa card, I will get an authorization request. If he has sufficient funds, I spend the appropriate amount of bitcoins to an address under my sole control, and then authorize the payment. Meanwhile, my customers can remove their funds at their discretion (and without my permission).
The reason 1-of-2 is better, is because now my customer can't claim that I stole his bitcoins. If there is only a single shared private key instead, he could spend the coins but claim that it was me who spent them. With a 1-of-2 wallet, it is clear who actually spent the coins.
Excellent reason, I did not think about that. Many thanks.
But the customer will only see you have as much control of the coins as (s)he has - so I don't think many customers will accept this as a solution.
I am not so much worried about that, the monthly paiement is just a convenience that the customer can use if he does not want to worry about paiement. In my case, the customer will still be able to pay himself.
Today, customers give their card number to companies quite easily. If they are stolen, they will be reimbursed. With bitcoin, the customer get the proof that the business with which he deals took the money without permission (thanks to the 1 of 2), so he can sue pretty easily and get money back.
